MIMO (multi-input multi-output) technology means a method of improving data transceiving efficiency by adopting multiple transmitting antennas and multiple receiving antennas instead of a single transmitting antenna and a single receiving antenna. In particular, this technology increases capacity or enhances performance using multiple antennas in a transmitting or receiving end of a wireless communication system. This MIMO technology may be called multi-antenna technology.
In order to support MIMO transmission, it may be able to use a precoding matrix to appropriately distribute transmission information to each antenna in accordance with a channel status and the like. In the conventional 3GPP (3rd generation partnership project) LTE (long term evolution) system, maximum 4 transmitting antennas are supported for downlink transmission and a corresponding precoding codebook is defined.